Testing of convex hyperbolic mirrors using a concave, spherical mirror was suggested by Hindle and has been in common use for a number of years. A point source is placed at one conjugate of the hyperbola and the center of curvature of the concave spherical mirror (Hindle Sphere) is placed at its second conjugate. The combination of the two mirrors produces an image of the point source back upon itself. The image can be analyzed using a variety of techniques, including interferometry, and the knife edge in the manner suggested by Foucault.